The PSLV, costing around Rs. 90 crore, blasted off from the Satish Dhawan Space Centre in Sriharikota, around 80 km from Chennai.

The Indian Space Research Organisation (Isro) has now completed its 100th mission since the launch of its first satellite, Aryabhata, in 1975 by a Russian rocket.

With a rich orange flame at its tail and plume of white smoke, PSLV-C21 ascended towards the sky amid cheers of Isro scientists and media team assembled at the launch centre.

People perched atop nearby buildings too clapped as the rocket went up.

Scientists at Isro's new mission control room were glued to their computer screens watching the rocket escape the earth's gravitational pull.

At around 18 minutes into the flight, PSLV-C21 delivered SPOT 6 and a few seconds later Proiteres into their intended polar orbits.

On the successful ejection of the satellites, scientists at mission control were visibly relieved and started clapping.

Manmohan Singh, who along with minister in Prime Minister's Office, V Narayanasamy, witnessed the launch, congratulated Isro scientists and engineers and EADS Astrium of France and Japan's Osaka Institute of Technology for the successful launch of their satellites.

"Questions are sometimes asked about whether a poor country like India can afford a space programme and whether the funds spent on space exploration, albeit modest, could be better utilised elsewhere.

"This misses the point that a nation's state of development is finally a product of its technological prowess," the Prime Minister said.

The remote sensing satellites send back pictures and other data.

SPOT 6 is the heaviest foreign satellite to be carried by a PSLV since 1999 when Isro started launching satellites of foreign agencies.

Proiteres will study powered flight of another satellite and observe Japan's Kansai district with a high-resolution camera.

Speaking to reporters later, Isro Chairman K. Radhakrishnan said discussions were on with the French space agency to carry SPOT 7, a similar remote sensing satellite slated for launch soon.

He said there were 13 more satellites of similar class and some other satellites could go as co-passengers to the main cargo that Isro/Antrix Corporation (Isro's commercial arm) would target.

Declining to reveal the carriage fee received from French and Japanese agencies for launching their satellites, Radhakrishnan said the mission revenue had recovered the rocket's cost.

Agreeing that there was a two-minute delay in the rocket's lift off (the scheduled time was 9.51am), Radhakrishnan said it was to avoid possible space debris impacts.

He said Isro had decided to set up a Multi Object Tracking Radar (MOTR) to track space debris and time its rocket launches precisely.

Isro was also planning to have a second vehicle (rocket) assembly building to increase launch frequency, he said.

Isro would also build two more communication satellites - GSAT 15 and GSAT 16 - to augment its transponder (transmitters that receive and send signals) capacity, he added.

Till date, Isro has successfully launched 27 foreign satellites and the Sunday mission took the tally to 29.